XPG requires insque() and remque() to work with linear lists and not just

circular lists.  Amazingly, they managed to extend the requirements to no
longer match the behavior of the VAX instructions they were modeled after,
so the trivial VAX ASM versions have to go.  Nice job breaking it, X/Open!
Based on a diff from enh (at) google.com
ok miod@

src/lib/libc/stdlib/Makefile.inc

@@ -1,13 +1,14 @@
-#	$OpenBSD: Makefile.inc,v 1.53 2014/05/08 21:43:49 deraadt Exp $
+#	$OpenBSD: Makefile.inc,v 1.54 2014/08/15 04:14:36 guenther Exp $
 
 # stdlib sources
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/stdlib ${LIBCSRCDIR}/stdlib
 
 SRCS+=	a64l.c abort.c atexit.c atoi.c atof.c atol.c atoll.c bsearch.c \
 	cfree.c exit.c ecvt.c gcvt.c getenv.c getopt_long.c \
-	getsubopt.c hcreate.c heapsort.c imaxabs.c imaxdiv.c l64a.c llabs.c \
-	lldiv.c lsearch.c malloc.c reallocarray.c merge.c posix_pty.c \
-	qsort.c radixsort.c rand.c random.c realpath.c setenv.c strtoimax.c \
+	getsubopt.c hcreate.c heapsort.c imaxabs.c imaxdiv.c insque.c \
+	l64a.c llabs.c lldiv.c lsearch.c malloc.c reallocarray.c \
+	merge.c posix_pty.c qsort.c radixsort.c rand.c random.c \
+	realpath.c remque.c setenv.c strtoimax.c \
 	strtol.c strtoll.c strtonum.c strtoul.c strtoull.c strtoumax.c \
 	system.c tfind.c tsearch.c _rand48.c drand48.c erand48.c jrand48.c \
 	lcong48.c lrand48.c mrand48.c nrand48.c seed48.c srand48.c qabs.c \
@@ -24,12 +25,6 @@ SRCS+=	abs.c div.c labs.c ldiv.c
 SRCS+=	abs.c div.c labs.c ldiv.c
 .endif
 
-.if (${MACHINE_CPU} == "vax")
-SRCS+=	insque.S remque.S
-.else
-SRCS+=	insque.c remque.c
-.endif
-
 MAN+=	a64l.3 abort.3 abs.3 alloca.3 atexit.3 atof.3 atoi.3 atol.3 atoll.3 \
 	bsearch.3 div.3 ecvt.3 exit.3 getenv.3 getopt.3 getopt_long.3 \
 	getsubopt.3 hcreate.3 imaxabs.3 imaxdiv.3 insque.3 labs.3 ldiv.3 \

src/lib/libc/stdlib/insque.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: insque.c,v 1.2 2005/08/08 08:05:36 espie Exp $	*/
+/*	$OpenBSD: insque.c,v 1.3 2014/08/15 04:14:36 guenther Exp $	*/
 
 /*
  *  Copyright (c) 1993 John Brezak
@@ -28,6 +28,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <stdlib.h>
 #include <search.h>
 
 struct qelem {
@@ -38,11 +39,16 @@ struct qelem {
 void
 insque(void *entry, void *pred)
 {
-	struct qelem *e = (struct qelem *) entry;
-	struct qelem *p = (struct qelem *) pred;
+	struct qelem *e = entry;
+	struct qelem *p = pred;
 
-	e->q_forw = p->q_forw;
-	e->q_back = p;
-	p->q_forw->q_back = e;
-	p->q_forw = e;
+	if (p == NULL)
+		e->q_forw = e->q_back = NULL;
+	else {
+		e->q_forw = p->q_forw;
+		e->q_back = p;
+		if (p->q_forw != NULL)
+			p->q_forw->q_back = e;
+		p->q_forw = e;
+	}
 }

src/lib/libc/stdlib/remque.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: remque.c,v 1.2 2005/08/08 08:05:37 espie Exp $	*/
+/*	$OpenBSD: remque.c,v 1.3 2014/08/15 04:14:36 guenther Exp $	*/
 
 /*
  *  Copyright (c) 1993 John Brezak
@@ -28,6 +28,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <stdlib.h>
 #include <search.h>
 
 struct qelem {
@@ -38,7 +39,10 @@ struct qelem {
 void
 remque(void *element)
 {
-	struct qelem *e = (struct qelem *) element;
-	e->q_forw->q_back = e->q_back;
-	e->q_back->q_forw = e->q_forw;
+	struct qelem *e = element;
+
+	if (e->q_forw != NULL)
+		e->q_forw->q_back = e->q_back;
+	if (e->q_back != NULL)
+		e->q_back->q_forw = e->q_forw;
 }